1. Field of the Invention
The present invention relates to a proximity sensor, and more particularly to an optical proximity sensor and a manufacturing method thereof.
2. Description of Related Art
With reference to FIG. 6, a conventional optical proximity sensor 60 comprises a substrate 61, a metal cover 62, an LED (Light Emitting Diode) device 63 and a sensing device 64.
The metal cover 62 is mounted on the substrate 61 and has a division 620, two spaces 621 and two openings 622. The two spaces 621 are divided by the division 620. The two openings 622 are formed on a top surface of the metal cover 62 and respectively communicate with the two spaces 621. The LED device 63 and the sensing device 64 are respectively mounted in the two spaces 621. When an object 65 approaches the optical proximity sensor 60, the object 65 reflects the light generated from the LED device 63. The sensing device 64 then detects the reflected light from the object 65.
The optical proximity device 60 is preferably small in volume and the metal cover 62 is manufactured by metal stamping. However, to stamp a metal piece into the small-volume metal cover 62 is difficult and expensive.
With reference to another proximity sensor of U.S. Pat. No. 8,097,852, the proximity sensor is mainly manufactured through twice packaging as described below.
With reference to FIG. 7A, a first step is to mount an illuminant device 71 and a sensing device 72 on a lead frame 70 and to respectively form transparent gels 73 on the illuminant device 71 and the sensing device 72. The above-mentioned forming of the transparent gels 73 is called a first packaging.
With reference to FIG. 7B, a second step is to press a mold 74 on the transparent gels 73 after the two transparent gels 73 solidify. The mold 74 has two protrusions 740 respectively attaching to a top surface of the transparent gels 73.
With reference to FIG. 7C, a third step is to inject an encapsulant gel 75 between the mold 74 and the lead frame 70, called a second packaging. The encapsulant gel 75 packages the illuminant device 71 and the sensing device 72 for protecting them from wetness and pollution.
With reference to FIG. 7D, a fourth step is to remove the mold 74 after the encapsulant gel 75 solidifies. Two holes 750 are then formed in the encapsulant gel 75 at positions previously occupied by the protrusions 740. Hence, the illuminant device 71 can emits lights outward through the transparent gels 73 and the hole 750. The sensing device 72 can detect lights entering the holes 750 and the transparent gels 73.
However, with reference to FIG. 7C, in the step of injecting the encapsulant gel 75, the transparent gels 73 have already solidified. The mold 74 cannot over-press on the solidified transparent gels 73 in order to avoid damaging the illuminant device 71 and the sensing device 72, resulting in poor marginal adaptation. When the encapsulant gel 75 is being injected among the mold 74 and the lead frame 70 by a high injecting pressure, the encapsulant gel 75 may permeate through the protrusions 740 and the transparent gels 73. With reference to FIG. 7D, when the mold 74 is removed, residue encapsulant gel 751 may be left on the transparent gels 73.
The sensing device 72 is used to detect environmental light variances. When the sensing device 72 receives a reflected light emitted from the illuminant device 71 and is reflected by an object, the sensing device 72 detects light variances. Hence, it is important to keep the transparent gels 73 pure without the residue encapsulant gel 751 such that the illuminant device 71 can normally emit lights and the sensing device 72 can normally receive lights. However, the residue encapsulant gel 751 spoils the transparent gel 73 and the lights emitted from the illuminate 71 and received by the sensing device 72 are blocked, causing low sensing accuracy.